1. Field
This invention relates to a heat exchanger. The invention relates particularly, but not necessarily exclusively, to a heat exchanger for use in the cooling of furnaces of metalliferous smelters. It will readily be appreciated that the heat exchanger could be used in a wide range of other applications as well.
2. General Background
In metalliferous smelters and, in particular, aluminium smelters, the smelter comprises a plurality of pots or furnaces, each having a shell within which an electrolyte and molten metal are contained. Aluminium is produced by an electrolysis process and the temperature of the electrolyte can reach temperatures of approximately 1000° C. This results in substantially elevated temperatures on the shell of each pot. It is therefore necessary to reduce the temperature of these shells to protect the shell from corrosion and catastrophic failure.
In the past, this has been achieved by directing a cooling fluid, such as air, on to the shell at locations which have become excessively hot. This requires very large amounts of compressed air, is extremely inefficient and generates noise and dust hazards for the operators. Moreover, the air can only be applied in this way to the overheated localised parts of a furnace shell. The shell temperature for the great majority of furnaces is not cooled by this means and no overall smelter benefit is derived.
In another development (U.S. Pat. No. 6,251,237 to Bos et al), the installation of permanent ducting as an integral part of each shell has been proposed. Not only does this necessitate a complex conduit system but some form of forced driving of the fluid is required as well.
In addition, to modify smelters to cool them, it may, in certain circumstances, be necessary that each furnace first be shut down. This is economically disadvantageous as any down time of the smelter has adverse economic consequences. More importantly, when a furnace is shut down for any significant length of time, the electrolyte solidifies resulting in major start up procedures having to be effected in order to restart the furnace.